Growth rate vs. daily pH swing

[karimwassef]

I'm going to have to restart.

My skimmer outlet got partially clogged overnight while my skimmer was off. A snail managed to squeeze in there and get lodged against the flow when it kicked back on again. That raised my skimmer top level and caused it to overflow. I have an effluent overflow alarm but I was tinkering with it, so it was offline... perfect @!#!% timing.

I lost a lot of SW and my ATO kicked in. By morning, it had dropped my salinity from 30 to 27.

After cleaning up. I started to reset - so I took some measurements.

Salinity 27
Alk 9
Ca 520
Mg 1305

So, I decided to make a saltier than usual batch of SW. The most I could make up at one time is about 100g (my total tank is 660g), so I used my calculator and determined that I'd need almost a double salinity batch to get back to about 33.

I can make large changes with a separate reservoir that is valved off from the sump. I remove the water from it until it's dry, make new SW and then slowly open the valve after it's been thoroughly mixed.

I made the 100g at a salinity of 66 and just used my calculator to predict the other parameters based on a baseline of fresh Reef Crystals (Baseline @ 33 salinity - 10dKH, Ca 440, Mg 1260). That should have resulted in a total tank at 33 salinity, 10.8dKH, Ca 600, Mg 1540.

The Alk rise from 9 to ~11 was a little worrying, but it was going to move over a day and align with a higher salinity that should be able to hold more Ca and Alk.

If I'd measured the freshly made saltwater, I would have found out that this batch was not like the baseline.

The result after about a day of slowly letting the new water merge with the tank was a pretty significant change

Salinity 33
Alkalinity 12
Calcium 620
Magnesium 1600

That's a pretty healthy departure from my pre-water change conditions. Especially troubling was the high Alkalinity. I hope a rise from 9 to 12 in one day isn't going to be catastrophic, but we'll see.

Based on this result, I worked backwards and it looks like THIS batch of reef crystals was very alkaline and very high Mg (@ 33 salinity - 18dKH, Ca 545, Mg 1660).

Polyps closed up, but fish were unaffected. 24hrs later, everything looks ok and polyps extended again.

Given the magnitude of the change, I'll have to reset. I'll give it a week to see if there's any long term damage and pick it back up again.

NOTE TO SELF - GET THE EFFLUENT OVERFLOW ALARM WORKING AGAIN - and measure the primary three on large water changes...

two back to back unpredictable events...

 

[HighlandReefer]

The effect of pH, alkalinity, and calcium on hermatypic corals
By Christie D. Rajcic, B.S. July 2014

http://www.advancedaquarist.com/2014/7/corals

From it in part:

"Are reefkeepers striving for the right levels of pH, alkalinity, and calcium? Using PAM fluorometry, Christie D. Raji studies the effects of high and low levels of each of these parameters on hermatypic corals in a captive environment."

"Results

pH
There was a significant difference in the maximum potential quantum yield among species by pH (F = (3, 328) 15.1, p-value < 0.001), see Figure 2a; however, there was a weak relationship (r2 = 0.121), see Figure 3b. C. furcata and P. damicornis had a significant difference (p-value < 0.05), and P. decussata, showed no significant difference (p-value = 0.143). Among all species there was a noticeable peak in Fv/Fm around 8.2.

Alkalinity
The maximum potential quantum yield showed species-specific responses to changes in the alkalinity (F = (3, 328) 43.1, p-value < 0.001), see Figure 2b. Similar to pH, a weak relationship (r2 = 0.283) was observed (Figure 3a). Additionally, C. furcata and P.damicornis both had a significant difference (p-values < 0.001) in Fv/Fm, however P. decussata did not (p-value = 0.107).

Calcium
There was a significant difference in maximum potential quantum yield values among the calcium treatments of the three species (F = (3, 319) 17.0, p-value < 0.001), see Figure 2c. However, similar to pH and alkalinity there was a weak relationship (r2 = 0.134), see Figure 3c. Specifically there was a significant effect among C. furcata and P. damicornis (p-values < 0.001). Again, P. decussata was not significantly affected (p-value = 0.124). A noticeable minimum threshold of approximately 375 ppm was observed among all species."

"Ocean Acidification
While there were no significant changes observed in coral health between pH treatments, it is important to note that hydrochloric acid was used in place of carbon dioxide. While pH was altered, there was no net increase of carbonic acid, as projections indicate as a result of carbon dioxide sequestration. A decrease in pH is known to decrease the net calcification of hermatypic corals due to the reduction of alkalinity; however, photochemical efficiency showed no significant change during this study. This is important in that projected pH levels (i.e. 7.9) do not appear to significantly affect the photochemistry of zooxanthellae. This indicates the need for better understanding of the relationship between zooxanthellae and their coral host to accurately predict the changes in population dynamics that may result from ocean acidification.

Coral Aquaculture
As shown by Zartler (2012), individual coral species respond differently to changes in temperature within the recommended range for aquaculture. Similarly, this study shows that individual species respond differently to pH, alkalinity, and calcium. For instance, P. decussata and C. furcata are highly adaptive corals that have a small negative response in hostile water quality environments, and can be considered as ideal beginner corals. Whereas, P. damicornis has a smaller range of tolerance and would be more affected in the event of overdosing. This information can be used when determining the skill level required of an aquarist to maintain a specific species (easy/moderate/difficult), and should be considered when devising dosing procedures for aquaculture."

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It's one thing testing coral in nature & another when they are tested in marine aquariums, while introducing variation with different parameters. Interesting experiment you're doing.

 

[karimwassef]

Interesting article. Thanks.

Almost everyone seems to focus on a fixed value of pH, Alk, Ca instead of the variation around that baseline.

 

[tajaba]

just following up on this, did your research yield any result?

 

[karimwassef]

I had a monti nudi infestation - still working through it.

The growth on my montis is not uniform or steady, but still strong. I stopped measuring but I had it running June on a cycle 8.3 - 8.4 day to night.

I'll change it to flat 8.4 and measure the change.